Status detector for power supply, power supply, and initial characteristic extracting device for use with power supply

ABSTRACT

In a status detector for a power supply, a power supply, and an initial characteristic extracting device for use with the power supply, a measuring unit obtains measured values of at least current, voltage and temperature of the electricity accumulating unit. A processing unit executes status detection of the electricity accumulating unit by using the measured values and the characteristic information of the electricity accumulating unit which is stored in a memory unit. A discrepancy detecting unit detects the presence of a discrepancy away from a theoretical value when a result of the status detection is changed over a predetermined threshold or reversed with respect to the measured values. A modifying unit modifies the characteristic information depending on the detected discrepancy.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuing application of U.S. application Ser.No. 11/347,388, filed Feb. 6, 2009 now U.S. Pat. No. 7,622,894, whichclaims priority under 35 U.S.C. §119 to Japanese Patent Application No.2005-062073, filed Mar. 7, 2005, the entire disclosure of which areherein expressly incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a status detector for a power supply, apower supply, and an initial characteristic extracting device for usewith the power supply, each of which is suitable for detecting thestatus of a battery (accumulator).

2. Description of the Related Art

In power supplies, decentralized power storages, and electric vehiclesusing electricity accumulating units such as a lithium secondarybattery, a nickel-hydrogen battery, a lead-acid battery, and an electricdouble-layer capacitor, a status detector for detecting the status ofeach electricity accumulating unit is employed to ensure safe andeffective use of the electricity accumulating unit. The status of theelectricity accumulating unit includes, e.g., the state of charge (SOC)or the remaining capacity indicating to what extent the unit is chargedor how much dischargeable charges remain, and the state of health (SOH)or a deterioration level indicating how far the unit is deteriorated orrun down. In order to detect those states of the electricityaccumulating unit, it is also required to know characteristicinformation (such as internal DC resistance) of the electricityaccumulating unit beforehand.

SOC (State Of Charge) of a power supply used in portable equipment,electric vehicles, etc. can be detected by integrating currentdischarged from the fully charged state and calculating a ratio of theamount of charges remaining in the electricity accumulating unit (i.e.,the remaining capacity) to the amount of maximally chargeable charges(i.e., the fully charged capacity). In many of the electricityaccumulating units, however, because the fully charged capacity ischanged depending on SOH (State Of Health), temperature, etc., it isdifficult to accurately detect SOC, taking into account those changesdepending on time and environment as well.

To overcome such a difficulty, there are known techniques as follows.For example, JP-A-10-289734 (Patent Document 1) discloses that aninitial battery characteristic is modified in accordance with atemperature modification coefficient computed based on a batterytemperature and a deterioration modification coefficient computed basedon a battery deterioration, and the remaining capacity of a battery iscomputed based on not only the modified battery characteristic, but alsoa discharge current and a terminal voltage during discharge.

Also, JP-A-11-218567 (Patent Document 2) discloses that a deterioratedbattery characteristic is computed by modifying an initial batterycharacteristic based on respective relations to a temperaturemodification coefficient, an internal resistance deteriorationmodification coefficient, and a capacity deterioration modificationcoefficient.

JP-A-2000-166105 (Patent Document 3) discloses that the state of chargeis detected based on a charge or discharge current, the state ofaccumulated electricity is detected based on a voltage, and the state ofcharge is controlled in accordance with the detected results.

JP-A-2000-166109 (Patent Document 4) discloses that an electromotivevoltage is determined from a charge or discharge current and a voltage,and a charge characteristic is computed based on the relationshipbetween the electromotive voltage and the charge characteristic.

Further, JP-A-2001-85071 (Patent Document 5) discloses that atemperature of each of combined battery modules is estimated based on avoltage between respective two terminals and a current flowing througheach terminal.

SUMMARY OF THE INVENTION

However, the following problems are still left with the related art.According to the method disclosed in JP-A-10-289734, influences oftemperature and deterioration are taken into consideration as thetemperature modification coefficient and the deterioration modificationcoefficient, and parameters necessary for calculating the remainingcapacity are modified using those modification coefficients which havebeen obtained through complicated computing processes. Accordingly,there remain questions as to whether values of the modificationcoefficients are correct in themselves, and whether all batterycharacteristics are modified.

In addition, because some type of electricity accumulating unit hascharacteristics such as charge efficiency and memory effect, thosecharacteristics have to be also taken into consideration in themodification process to estimate the remaining capacity with highaccuracy. Moreover, because initial characteristics of electricityaccumulating units have individual differences, those individualdifferences have to be further taken into consideration in themodification process to estimate the remaining capacity with highaccuracy.

Stated another way, in order to perform the status detection, e.g., theestimation of the remaining capacity, with high accuracy, it is requiredto faithfully make modeling of characteristics of the electricityaccumulating unit and to take a plurality of parameters into account.Further, modification has to be performed in consideration of changes ofthose parameters depending on time and environment.

Thus, a great deal of time and labor are consumed to obtain initialcharacteristics and plural parameters of the electricity accumulatingunit and to acquire data of the modification coefficients. In spite ofprocessing being executed in a how complicated manner, however, theprocessing result falls within the scope of theory regarding batterycharacteristics or estimation based on a model, thus accompanying with aquestion as to whether the estimated result is correct with respect to atrue value.

An object of the present invention is to provide a status detector for apower supply, a power supply, and an initial characteristic extractingdevice for use with the power supply, each of which can detect thestatus of an electricity accumulating unit with high accuracy.

The present invention provides a status detector for a power supply,which can detect the status of an electricity accumulating unit withhigh accuracy.

According to one major aspect of the present invention, the statusdetector for the power supply comprises a measuring unit capable ofobtaining measured values of at least current, voltage and temperatureof electricity accumulating unit; a memory unit for storingcharacteristic information of the electricity accumulating unit; aprocessing unit for executing status detection of the electricityaccumulating unit by using the measured values and the characteristicinformation of the electricity accumulating unit which is stored in thememory unit; a discrepancy detecting unit for detecting the presence ofa discrepancy away from a theoretical value when a result of the statusdetection obtained by the processing unit is changed over apredetermined threshold or reversed with respect to the measured valuesobtained by the measuring unit; and a modifying unit for modifying thecharacteristic information stored in the memory unit depending on thediscrepancy detected by the discrepancy detecting unit.

Also, the present invention provides a power supply, which can detectthe status of an electricity accumulating unit with high accuracy.

According to another major aspect of the present invention, the powersupply comprises an electricity accumulating unit capable of beingcharged and discharged; a measuring unit for obtaining information ofthe electricity accumulating unit during charge and discharge; and astatus detecting unit for detecting status of the electricityaccumulating unit, the status detecting unit comprising: a measuringunit capable of obtaining measured values of at least current, voltageand temperature of the electricity accumulating unit; a memory unit forstoring characteristic information of the electricity accumulating unit;a processing unit for executing status detection of the electricityaccumulating unit by using the measured values and the characteristicinformation of the electricity accumulating unit which is stored in thememory unit; a discrepancy detecting unit for detecting the presence ofa discrepancy away from a theoretical value when a result of the statusdetection obtained by the processing unit is changed over apredetermined threshold or reversed with respect to the measured valuesobtained by the measuring unit; and a modifying unit for modifying thecharacteristic information stored in the memory unit depending on thediscrepancy detected by the discrepancy detecting unit.

Further, the present invention provides an initial characteristicextracting device for use with a power supply, which can detect thestatus of an electricity accumulating unit with high accuracy.

According to still another major aspect of the present invention, theinitial characteristic extracting device for use with the power supplycomprises an electricity accumulating unit capable of being charged anddischarged; a measuring unit for obtaining information of theelectricity accumulating unit during charge and discharge; and a statusdetecting unit for detecting status of the electricity accumulatingunit, the status detecting unit comprising: a measuring unit capable ofobtaining measured values of at least current, voltage and temperatureof the electricity accumulating unit; a memory unit for storingcharacteristic information of the electricity accumulating unit; aprocessing unit for executing status detection of the electricityaccumulating unit by using the measured values and the characteristicinformation of the electricity accumulating unit which is stored in thememory unit; a discrepancy detecting unit for detecting the presence ofa discrepancy away from a theoretical value when a result of the statusdetection obtained by the processing unit is changed over apredetermined threshold or reversed with respect to the measured valuesobtained by the measuring unit; and a modifying unit for modifying thecharacteristic information stored in the memory unit depending on thediscrepancy detected by the discrepancy detecting unit, the initialcharacteristic extracting device further comprising acharging/discharging device for charging and discharging the electricityaccumulating unit in accordance with a predetermined pulse pattern, thecharging/discharging device performing charge and discharge of theelectricity accumulating unit, the measuring unit measuring theinformation of the electricity accumulating unit during the charge andthe discharge, the processing unit detecting the status of theelectricity accumulating unit by using the measured values and thecharacteristic information of the electricity accumulating unit which isstored in the memory unit, the discrepancy detecting unit detecting thepresence of a discrepancy of the detected status away from thetheoretical value, and the modifying unit modifying the characteristicinformation such that the characteristic information is converged withina certain range and the converged characteristic information isextracted as an initial characteristic of the electricity accumulatingunit.

According to the present invention, it is possible to detect the statusof the electricity accumulating unit with high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a power supplyaccording to a first embodiment of the present invention;

FIG. 2 is a flowchart showing processing procedures executed by a statusdetecting unit used in the power supply according to the firstembodiment of the present invention;

FIG. 3 is a circuit diagram showing an equivalent circuit of anelectricity accumulating unit used in the power supply according to thefirst embodiment of the present invention;

FIG. 4 is a graph for explaining the characteristic information betweenOCV (Open Circuit Voltage) and SOC (State Of Charge) in the power supplyaccording to the first embodiment of the present invention;

FIGS. 5A and 5B are charts for explaining changes of current and SOCduring charge in the power supply according to the first embodiment ofthe present invention;

FIG. 6 is a graph showing SOC and allowable currents of the electricityaccumulating unit in the power supply according to the first embodimentof the present invention;

FIG. 7 is a flowchart showing the operation of a discrepancy detectingunit in a power supply according to a second embodiment of the presentinvention;

FIG. 8 is a block diagram showing the configuration of a processing unitin a status detecting unit used in a power supply according to a thirdembodiment of the present invention;

FIG. 9 is a graph for explaining temperature-dependent changes ofinternal DC resistance of an electricity accumulating unit used in thepower supply according to the third embodiment of the present invention;

FIG. 10 is a block diagram showing the configuration of a power supplyaccording to a fourth embodiment of the present invention;

FIGS. 11A, 11B and 11C are graphs for explaining changes of SOC when anelectricity accumulating unit in the power supply according to thefourth embodiment of the present invention is deteriorated;

FIG. 12 is a flowchart showing processing procedures executed by adeterioration determining unit used in the power supply according to thefourth embodiment of the present invention;

FIG. 13 is a block diagram showing the configuration of an initialcharacteristic extracting device for use with a power supply accordingto a fifth embodiment of the present invention;

FIG. 14 is a flowchart showing processing procedures executed by acharging/discharging device in the initial characteristic extractingdevice for use with the power supply according to the fifth embodimentof the present invention;

FIG. 15 is a chart for explaining the charging/-discharging device inthe initial characteristic extracting device for use with the powersupply according to the fifth embodiment of the present invention;

FIG. 16 is a block diagram showing the configuration of a second initialcharacteristic extracting device for use with a power supply accordingto a sixth embodiment of the present invention;

FIGS. 17A and 17B are charts for explaining an initial characteristicextracting method in the power supply according to the sixth embodimentof the present invention;

FIG. 18 is a block diagram showing the configuration of a third initialcharacteristic extracting device for use with a power supply accordingto a seventh embodiment of the present invention;

FIG. 19 is a chart for explaining an initial characteristic extractingmethod in the power supply according to the seventh embodiment of thepresent invention; and

FIG. 20 is a block diagram showing the configuration of a fourth initialcharacteristic extracting device for use with a power supply accordingto an eighth embodiment of the present invention;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The configuration and operation of a power supply according to a firstembodiment of the present invention will be described below withreference to FIGS. 1-6.

The configuration of the power supply according to this embodiment willbe first described with reference to FIG. 1.

FIG. 1 is a block diagram showing the configuration of the power supplyaccording to the first embodiment of the present invention.

The power supply of this embodiment comprises a status detecting unit100, an electricity accumulating unit 200, a measuring unit 300, and anoutput unit 400. The electricity accumulating unit 200 serves toaccumulate electricity and discharge the accumulated electricity, and itis, e.g., a lithium secondary battery. This embodiment can also beapplied to the case of using, as the electricity accumulating unit 200,other similar device with the function of storing electricity, such as anickel-hydrogen battery, a lead-acid battery, and an electricdouble-layer capacitor. The electricity accumulating unit 200 may be asingle cell or may have a modular structure including a plurality ofsingle cells combined with each other.

The measuring unit 300 is constituted by sensors and electrical circuitsfor obtaining information (such as a voltage V, a current I, and atemperature T) of the electricity accumulating unit 200.

The status detecting unit 100 comprises a processing unit 110, adiscrepancy detecting unit 120, a memory unit 130, and a modifying unit140.

The processing unit 110 computes SOC (State Of Charge) of theelectricity accumulating unit 200 based on measured values (V, I, T)obtained from the measuring unit 300 and characteristic information(including a polarization voltage Vp and an internal DC resistance R) ofthe electricity accumulating unit 200, which is read out of the memoryunit 130.

The processing unit 110 is constituted by, e.g., a microprocessor or acomputer. An SOC computing method executed by the processing unit 110will be described later with reference to FIGS. 3 and 4.

The discrepancy detecting unit 120 monitors whether there is such adiscrepancy that the result obtained by the processing unit 110 is awayfrom a theoretical value, based on the measured value (I) obtained fromthe measuring unit 300 and the SOC computed by the processing unit 110.If the result obtained by the processing unit 110 is away from thetheoretical value, this is detected as being a discrepancy. A practicaldiscrepancy detecting method executed by the discrepancy detecting unit120 will be described later with reference to FIGS. 5 and 6.

The modifying unit 140 modifies the characteristic information (e.g.,the polarization voltage Vp and the internal DC resistance R) stored inthe memory unit 130. The modifying unit 140 may be started only when thediscrepancy detecting unit 120 detects a discrepancy away from thetheoretical value, or it may be started regardless of whether there is adiscrepancy away from the theoretical value.

When the modifying unit 140 is started regardless of whether there is adiscrepancy away from the theoretical value, it modifies thecharacteristic information using a predetermined modification amount ifthe discrepancy detecting unit 120 detects a discrepancy away from thetheoretical value. If there is no discrepancy away from the theoreticalvalue, the characteristic information is modified with the modificationamount set to 0. Also, the modifying unit 140 modifies thecharacteristic information depending on the nature of a discrepancy awayfrom the theoretical value, which has been detected by the discrepancydetecting unit 120. The operation of the modifying unit 140 will bedescribed later.

The memory unit 130 stores the characteristic information that can beobtained from the electricity accumulating unit 200 in advance, such asthe internal DC resistance, the polarization voltage, the chargeefficiency, the allowable current, and the fully charged capacity. Theseitems of the characteristic information may have characteristic valuesfor each of charge and discharge, or may have values depending on thestatus of the electricity accumulating unit 200, such as SOC ortemperature. As an alternative, each item of the characteristicinformation may be set to one value common to all states of theelectricity accumulating unit 200.

The memory unit 130 is formed of any suitable memory, e.g., a flashmemory, EEPROM, or a magnetic disk. The memory unit 130 may be providedexternally of the processing unit 110, or may be an internal memoryincorporated inside the processing unit 110. In addition to thecharacteristic information of the electricity accumulating unit 200, thememory unit 130 may store processing procedures for detecting the statusof the electricity accumulating unit 200.

The memory unit 130 may be removal. When the memory unit 130 is maderemoval, the characteristic information and the processing procedurescan be easily changed by replacing the memory unit 130. Further, bypreparing a plurality of replaceable memory units 130 and storing thecharacteristic information and the processing procedures in those memoryunits 130 in a distributed way, it is possible to more finely update thecharacteristic information and the processing procedures.

The output unit 400 outputs the SOC obtained by the processing unit 110,etc. to the exterior.

The operation of the status detecting unit 100 in the power supply ofthis embodiment will be described below with reference to FIGS. 2-6.

Overall processing executed by the status detecting unit 100 in thepower supply of this embodiment will be described with reference to FIG.2.

FIG. 2 is a flowchart showing processing procedures executed by thestatus detecting unit used in the power supply according to the firstembodiment of the present invention.

In step S10 of FIG. 2, the processing unit 110 executes status detectionby computing SOC of the electricity accumulating unit 200 based on themeasured values (V, I, T) of the electricity accumulating unit 200 andthe characteristic information (including the polarization voltage Vpand the internal DC resistance R) of the electricity accumulating unit200, which is read out of the memory unit 130.

A description is here made of processing procedures of the processingunit 110 in the status detecting unit 100 of this embodiment withreference to FIGS. 3 and 4.

FIG. 3 is a circuit diagram showing an equivalent circuit of theelectricity accumulating unit used in the power supply according to thefirst embodiment of the present invention. FIG. 4 is a graph forexplaining the characteristic information between OCV (Open CircuitVoltage) and SOC (State Of Charge) in the power supply according to thefirst embodiment of the present invention.

FIG. 3 shows an equivalent circuit of the electricity accumulating unit200. The electricity accumulating unit 200 is represented by anin-series connection containing a pair of an impedance Z and acapacitance component C connected in parallel, an internal DC resistanceR, and an electromotive force OCV.

When a current I is applied to the electricity accumulating unit 200, aninter-terminal voltage (CCV; Closed Circuit Voltage) of the electricityaccumulating unit 200 is expressed by the following formula (1);CCV=OCV+I·R+Vp  (1)In this formula, Vp represents the polarization voltage and correspondsto a voltage across the pair of the impedance Z and the capacitancecomponent C connected in parallel.

The electromotive force OCV is used for computing SOC, but it cannot bedirectly measured in a condition that the electricity accumulating unit200 is being charged or discharged. Therefore, the electromotive forceOCV is computed by subtracting an IR drop and the polarization voltageVp from the electromotive force CCV as expressed by the followingformula (2).OCV=CCV−I·R—Vp  (2)Here, the internal DC resistance R and the polarization voltage Vp canbe obtained from the characteristic information stored in the memoryunit 130. The internal DC resistance R and the polarization voltage Vphave values depending on the SOC, temperature, etc. of the electricityaccumulating unit 200. The current value I is obtained from a valuemeasured by the measuring unit 300.

FIG. 4 shows the relationship between the electromotive force OCV andSOC. After the electromotive force OCV is computed using the currentvalue I, the internal DC resistance R and the polarization voltage Vpbased on the formula (2), the SOC of the electricity accumulating unit200 can be estimated from the characteristic information between theelectromotive force OCV and SOC, which has been obtained in advance.

The processing unit 110 transmits the thus-estimated SOC to thediscrepancy detecting unit 120.

Returning to FIG. 2, in step S20, the discrepancy detecting unit 120monitors whether there is a discrepancy away from the theoretical value,based on the SOC received from the processing unit 110 and the measuredvalue (I) received from the measuring unit 300. If there is nodiscrepancy, the control flow proceeds to step S50, and if there is adiscrepancy, the control flow proceeds to step S30.

A description is here made of processing procedures of the discrepancydetecting unit 120 in the status detecting unit 100 of this embodimentwith reference to FIGS. 5 and 6.

FIGS. 5A and 5B are charts for explaining changes of current and SOCduring charge in the power supply according to the first embodiment ofthe present invention.

FIG. 5A shows change of the current, and FIG. 5B shows change of the SOCobtained by the processing unit 110. As shown in FIG. 5A, when charge tothe electricity accumulating unit 200 is started at a time t1, thecurrent I changes from 0 to a positive value. Correspondingly, as shownin FIG. 5B, the result (SOC) of the status detection computed by theprocessing unit 110 starts to increase from the time t1.

At that time, the discrepancy detecting unit 120 monitors whether theincrease of SOC does not exceed a predetermined threshold Th. If the SOChas increased over the predetermined threshold Th as shown in FIG. 5B,the discrepancy detecting unit 120 determines that the change of SOC isexcessive and is discrepant away from the theoretical value.

The foregoing is related to the state of starting the charge. When thecurrent value I is reduced from 0 in the discharge state, thediscrepancy detecting unit 120 monitors a decrease of SOC, i.e., adecrease of the result computed by the processing unit 110. If the SOChas decreased over the predetermined threshold Th, the discrepancydetecting unit 120 determines that the change of SOC is discrepant awayfrom the theoretical value, thus indicating detection of a discrepancy.

The threshold Th used for determining whether the change of SOC isexcessive is obtained using an allowable maximum charge or dischargecurrent value Imax and a fully charged capacity Qmas, which are derivedfrom the performance of the electricity accumulating unit 200, based onthe following formula (3)Th=ΔSOCmax=100×Imax/Qmax  (3)Looking from the specific performance of the electricity accumulatingunit 200, the SOC will never change over ΔSOCmax no matter whatcondition is. Accordingly, if the computed SOC has increased ordecreased over ΔSOCmax, this can be determined as indicating adiscrepancy away from the theoretical value.

The case of changing the threshold Th depending on the performance andstatus of the electricity accumulating unit 200 will be described withreference to FIG. 6.

FIG. 6 is a graph showing SOC and allowable currents of the electricityaccumulating unit in the power supply according to the first embodimentof the present invention.

As shown in FIG. 6, as the SOC increases, an allowable charge current isincreased, while an allowable discharge current is decreased. Assumingan upper limit voltage and a lower limit voltage of the electricityaccumulating unit 200 to be Vmax and Vmin, an allowable charge currentIcmax and an allowable discharge current Idmax are expressed by thefollowing formulae (4) and (5), respectively;Icmax=(Vmax−OCV)/Rz  (4)Idmax=(OCV−Vmin)/Rz  (5)wHere Rz represents an equivalent impedance of R, Z and C shown in FIG.3.

An SOC maximum increase amount ΔSOCcmax during charge and an SOC maximumdecrease amount ΔSOCdmax during discharge depending on the performance,temperature and SOC of the electricity accumulating unit 200 areobtained using the fully charged capacity Qmax of the electricityaccumulating unit 200 based on the following formulae (6) and (7),respectively:ΔSOCcmax=100×Icmax/Qmax  (6)ΔSOCdmax=100×Idmax/Qmax  (7)

The SOC of the electricity accumulating unit 200 will never increaseover ΔSOCcmax during charge and it will never decrease over ΔSOCdmaxduring discharge. Accordingly, the discrepancy detecting unit 120 canuse each of ΔSOCcmax and ΔSOCdmax as the threshold Th that is variabledepending on the performance, temperature and SOC of the electricityaccumulating unit 200. In other words, a discrepancy can be detected byusing the SOC maximum increase amount ΔSOCcmax during charge and the SOCmaximum decrease amount ΔSOCdmax during discharge not only when thecurrent is stepwisely changed as in the state of starting charge, asshown in FIG. 5, but also when the current is moderately changed.

The above-described manner of deciding the threshold Th represents thecase where the performance of the electricity accumulating unit 200 istaken into consideration. By additionally considering the maximumallowable charge and discharge currents depending on a system in whichthe electricity accumulating unit 200 is used as the power supply, thethreshold Th can be decided with higher reliability. To describe amanner of deciding the threshold Th during discharge, for example, evenwith the maximum allowable discharge current of the electricityaccumulating unit itself being 200 A, when the electricity accumulatingunit is used in an actual system in the form of a vehicle, a maximumcurrent value used in the system is 100 A in some case. In that case,the threshold Th can be decided by using 100 A as the maximum allowabledischarge current. To describe a manner of deciding the threshold Thduring charge, even with the maximum allowable charge current of theelectricity accumulating unit itself being 200 A, when the electricityaccumulating unit is used in an actual system in the form of a vehicle,a maximum generation current of a generator motor (M/G) used as analternator or a generator is 100 A in some case. In that case, thethreshold Th can be decided by using 100 A as the maximum allowablecharge current.

Returning to FIG. 2, if a discrepancy is detected in step S20, themodifying unit 140 modifies the characteristic information and storesthe modified characteristic information in the memory unit 130 in stepS30.

To cope with the discrepancy away from the theoretical value, themodifying unit 140 increases the value of the internal DC resistance Rand stores a modified internal DC resistance R′ as new characteristicinformation in the memory unit 130 to be used from the subsequentprocessing as the new characteristic information.

The internal DC resistance R may be modified by increasing theresistance value by 1%, or by a minimum unit for the value representingthe characteristic information. As another method, a modification amountmay be set to be larger as the discrepancy away from the theoreticalvalue is increased, and to be smaller as the discrepancy away from thetheoretical value is decreased. The minimum unit for the valuerepresenting the characteristic information means a minimum unitcorresponding to a digit of the internal DC resistance, which can bedistinctively stored in the memory unit 130. Assuming a minimum value ofthe internal DC resistance to be, e.g., 0.1 mΩ, the internal DCresistance is increased in units of 0.1 mΩ.

When it is desired to dynamically change the modification, the followingmethod can be used, by way of example. If the SOC is changed over thethreshold Th, the state of charge SOCth is obtained using the state ofcharge SOCold in the preceding cycle based on the following formula (8):SOCth=SOCold+Th  (8)

An electromotive force OCVth corresponding to the state of charge SOCthcan be obtained from the relationship between the electromotive forceOCV and SOC shown in FIG. 4. By using the obtained OCVth, the formula(2) can be rewritten to the following formula (9):OCVth=CCV−I·Rth−Vp  (9)By rearranging the formula (9), Rth providing change of SOC, which willnot exceed the threshold Th, can be expressed by the following formula(10):Rth=(CCV−OCVth−Vp)/I  (10)

The modifying unit 140 modifies the internal DC resistance so that Rthexpressed by the formula (10) is obtained. Thus, the modification amountof the characteristic information can be changed in a dynamic manner.

The operation of the discrepancy detecting unit 120 will be describedbelow in connection with the case where the current value I measured bythe measuring unit 300 indicates charge and the result of the statusdetection executed by the processing unit 110 shows a decrease of SOC,or the case where the current value indicates discharge and the resultof the status detection shows an increase of SOC.

When the current value I of the electricity accumulating unit 200measured by the measuring unit 300 indicates charge and the result ofthe status detection executed by the processing unit 110 shows adecrease of SOC, i.e., “reversal”, the discrepancy detecting unit 120detects such a condition to be a discrepancy away from the theoreticalvalue. Also, when the current value I measured by the measuring unit 300indicates discharge and the result of the status detection shows anincrease of SOC, i.e., “reversal”, the discrepancy detecting unit 120similarly detects such a condition to be a discrepancy away from thetheoretical value.

The discrepancy detecting unit 120 may determine the detection of adiscrepancy in the case where the SOC shows the reversal even just alittle with respect to the measured current value, or may determine thedetection of a discrepancy with a margin allowing the reversal of SOC upto a predetermined value set within the range not exceeding thethreshold Th.

When the reversal of SOC is detected, the modifying unit 140 makesmodification to decrease the value of the internal DC resistance R. Aninternal DC resistance R′ modified by a predetermined amount is storedas new characteristic information in the memory unit 130, and the storednew characteristic information is used from the subsequent processing.

Table 1, given below, lists the operation of the discrepancy detectingunit 120 to detect a discrepancy away from the theoretical value, thecause of the discrepancy, and a modification action executed by themodifying unit 140 to overcome the discrepancy. As seen from Table 1,the discrepancy detecting unit 120 detects, as a discrepancy away fromthe theoretical value, the excessive change of SOC caused by too small Rand the reversal of SOC caused by too large R, and the modifying unit140 modifies R depending on the nature of the discrepancy. Accordingly,the status detection of the electricity accumulating unit 200 can beperformed by using R that causes neither the excessive change of SOC northe reversal of SOC.

TABLE 1 Operation of discrepancy Modification action of detecting unitCause modifying unit detect excessive too small R increase R change ofSOC detect reversal of SOC too large R decrease R

Returning to FIG. 2, in step S40, the processing unit 110 detects thestatus of the electricity accumulating unit 200 again by using the newcharacteristic information so that the result of the status detection isobtained with higher accuracy.

Then, in step S50 of FIG. 2, the obtained result of the status detectionis transmitted to the output unit 400 and is outputted to the exteriorfrom the output unit 400.

In the above description, the discrepancy detecting unit 120 and themodifying unit 140, shown in FIG. 1, may be constituted by separatemicroprocessors or computers. As an alternative, the discrepancydetecting unit 120 and the modifying unit 140 may be realized with onemicroprocessor or computer that executes the processing of both theunits 120 and 140 together. The processing unit 110, the discrepancydetecting unit 120, and the modifying unit 140 are interconnected viacommunication units capable of transferring information and commandsamong them.

While the discrepancy detecting unit 120 and the modifying unit 140 areshown in FIG. 1 as being installed externally of the processing unit110, those units may be constituted in the forms of program modules orsubroutines executing the above-described processing procedures, and maybe realized with one processing sequence containing the processingprocedures of both the discrepancy detecting unit 120 and the modifyingunit 140 together. In that case, the discrepancy detecting unit 120 andthe modifying unit 140 are stored as software in the memory unit 130 andexecuted by the processing unit 110.

The output unit 400 comprises LAN, CAN, radio LAN or short-range radiocommunication utilizing the so-called CSMA/CD system, or a device fortransferring an ON-OFF signal, such as a photocoupler or a relay, and anassociated circuit. The output unit 400 may use wired communication orradio communication. A display unit, such as a display monitor, may beused as the output unit 400 to display only the result of the currentstatus detection or to display a time-serial graph in which the resultsof the current and past status detections are indicated together.

Further, by employing a microcomputer in which an A/D converter, a flashmemory, a microprocessor and a communication circuit are constituted onthe same device, the measuring unit 300, the memory unit 130, theprocessing unit 110, the discrepancy detecting unit 120, the modifyingunit 140, and the output unit 400 used in this embodiment can beconstituted on the same device. Additionally, those units can be sharedby another control unit.

According to this embodiment, as described above, when the discrepancydetecting unit 120 detects the excessive change of SOC, the modificationto increase the internal DC resistance R is performed, and when thediscrepancy detecting unit 120 detects the reversal of SOC, themodification to decrease the internal DC resistance R is performed. As aresult, the status of the electricity accumulating unit 200 can bedetected with high accuracy in spite of parameters being changeddepending on time and environment.

The configuration and operation of a power supply according to a secondembodiment of the present invention will be described below withreference to FIGS. 1 and 7.

FIG. 7 is a flowchart showing the operation of a discrepancy detectingunit in the power supply according to the second embodiment of thepresent invention;

The overall configuration of the power supply according to thisembodiment is the same as that shown in FIG. 1. In this embodiment,processing procedures executed by the discrepancy detecting unit 120differs from those shown in FIG. 2.

After charge or discharge of the electricity accumulating unit 200 hasfinished, i.e., when the current value among the measured values hascome into a state indicating 0 A, it is normal that the SOC will notchange in environment where self-discharge is negligible. In view ofthat fact, the discrepancy detecting unit 120 monitors the SOC obtainedby the processing unit 110 after the charge or discharge has finished.If a change is found in the estimated SOC, this is detected asindicating a discrepancy away from the theoretical value.

A practical discrepancy detecting method executed by the discrepancydetecting unit 120 will be described below with reference to FIG. 7.

In step S100, the discrepancy detecting unit 120 set 0 in a counterprepared for counting the number of estimation results of SOC.

Then, in step S110, the discrepancy detecting unit 120 monitors thecurrent value among the measured values, and when the current value hasbecome 0 A, it determines that the charge or discharge of theelectricity accumulating unit 200 has finished.

Then, in step S120, the result of detecting the status of theelectricity accumulating unit 200 after determination that the charge ordischarge has finished, is stored in, e.g., a rewritable memory withinthe processing unit 110. In step S130, a value of the counter isincremented by one. At this time, the value set in the counter is 1.

Then, in step S140, the discrepancy detecting unit 120 monitors whetherthe counter value exceeds a predetermined threshold that has beenprepared in advance. If the counter value does not exceed thepredetermined threshold, the control flow returns to step S110. In stepS110, the present status of the electricity accumulating unit 200 ismonitored, and if neither charge nor discharge is being performed, theresult of detecting the status of the electricity accumulating unit 200is stored in addition to the previously stored result. The counter valueis further incremented by one to become 2 at this time. Theabove-described procedures are repeated until the counter value exceedsthe predetermined threshold, while successively storing the estimationresults of SOC after the end of the charge and discharge.

If the counter value exceeds the predetermined threshold, thediscrepancy detecting unit 120 analyzes, in step S150, the pluralresults of the status detection which have been stored in the memory,thereby confirming a change of SOC in the condition where theelectricity accumulating unit 200 is under neither charge nor discharge.Because the results stored in the memory correspond to the conditionwhere the electricity accumulating unit 200 is under neither charge nordischarge, it is normal that the change of SOC is not found.Accordingly, if the change of SOC is found, the discrepancy detectingunit 120 determines that there occurs a discrepancy away from thetheoretical value.

If there occurs a discrepancy, the modifying unit 140 modifies thepolarization voltage Vp in step S160.

The threshold is set to a value of 2 or more. When the threshold is setto 2, care should be paid because of a possibility that the change ofSOC caused by a sensing error or the like may be detected as indicatinga discrepancy away from the theoretical value.

The modifying unit 140 may be started only when the discrepancydetecting unit 120 detects a discrepancy away from the theoreticalvalue, or it may be always started even when no discrepancy is detected.In the latter case, the modifying unit 140 modifies the polarizationvoltage Vp with a modification amount set to 0 when no discrepancy isdetected, and it modifies the polarization voltage Vp by a predeterminedmodification amount when a discrepancy is detected.

If the measured value other than the current of 0 A is received beforethe counter value exceeds the predetermined threshold, i.e., if thecharge or discharge of the electricity accumulating unit 200 is startedbefore the same, the stored results of the status detection is erasedand the counter value is reset to 0. When the current of 0 A is detectednext, the above-described processing is executed in a similar way.

A description is now made of a discrepancy detecting method executed bythe discrepancy detecting unit 120 when the counter value exceeds thepredetermined threshold. When the counter value exceeds thepredetermined threshold, the discrepancy detecting unit 120 analyzes thetwo or more estimation results of SOC stored in the memory, and confirmsa time-serial change of SOC. The time-serial change of SOC can be formedby using, e.g., the least square method. More specifically, byapproximating two or more values of SOC with a linear line based on theleast square method, the time-serial change of SOC can be expressed by agradient k of the linear line. As an alternative, the time-serial changeof SOC may be confirmed by totalizing time-serial change amounts of thestored estimation results of SOC, dividing the total change amount bythe number of the stored estimation results of SOC to obtain an averagechange amount of SOC, and defining the average change amount as a changek of SOC.

Table 2, given below, lists the change k of SOC, which represents adiscrepancy away from the theoretical value after the end of charge anddischarge, and the modification of the polarization voltage Vp, which isexecuted by the modifying unit 140 to overcome the discrepancy.

TABLE 2 Charge Detection of k > 0 Too large Vp Decrease Vp ChargeDetection of k < 0 Too small Vp Increase Vp Discharge Detection of k > 0Too small Vp Increase Vp Discharge Detection of k < 0 Too large VpDecrease Vp

Thus, the status of the electricity accumulating unit 200 can bedetected using Vp that causes neither an increase of SOC nor a decreaseof SOC after the end of charge and discharge.

According to this embodiment, as described above, since the polarizationvoltage Vp is modified using the gradient k, the SOC estimation can beperformed with high accuracy.

The configuration and operation of a power supply according to a thirdembodiment of the present invention will be described below withreference to FIGS. 1, 8 and 9.

FIG. 8 is a block diagram showing the configuration of a processing unitin a status detecting unit used in the power supply according to thethird embodiment of the present invention. FIG. 9 is a graph forexplaining temperature-dependent changes of internal DC resistance of anelectricity accumulating unit used in the power supply according to thethird embodiment of the present invention.

The overall configuration of the power supply according to thisembodiment is the same as that shown in FIG. 1. In this embodiment, theprocessing unit in the status detecting unit is constituted as shown inFIG. 8 described below.

A state-of-charge SOCv detecting unit 110 corresponds to the processingunit 110 in FIG. 1 and estimates SOC based on the graph of FIG. 4 byusing the OCV obtained from the formula (2).

A state-of-charge SOCi detecting unit 112 obtains, from a currentsensor, a current I charged to or discharged from the electricityaccumulating unit 200 and calculates SOC based on the following formula(11):SOCi=SOC+100×∫I/Qmax  (11)

An IR error detecting unit 114 calculates R·I by multiplying the currentvalue I by the internal DC resistance R, thus obtaining an influence oferror generated. A weight deciding unit 116 decides a weight (1/(1+R·I)for SOCv and SOCi based on the error influence R·I obtained by the IRerror detecting unit 114.

In general, each of detected results of voltage, current and temperaturemeasured using sensors includes a substantially constant random error.Also, a current sensor generally has poorer accuracy than a voltagesensor. Therefore, the larger the current flowing through theelectricity accumulating unit 200, the larger is an error contained inthe current value I measured by the current sensor.

When obtaining the internal DC resistance R from the characteristicinformation, if the internal DC resistance R is derived corresponding tothe temperature T, the internal DC resistance R contains an errorbecause the temperature T obtained from a temperature sensor contains anerror.

Further, when the electricity accumulating unit 200 has a modularstructure in combination of plural units, the internal DC resistance Ralso contains an error due to variations in performance of individualelectricity accumulating units 200.

As shown in FIG. 9, the electricity accumulating unit 200 generally hassuch a tendency that the internal DC resistance R is relatively high ata lower value of SOC, and the value of the internal DC resistance R isincreased as the temperature of the electricity accumulating unit 200lowers. Also, the value of the internal DC resistance R is increasedwith deterioration of the electricity accumulating unit 200. The largervalue of the internal DC resistance R increases an error containedtherein.

The IR error detecting unit 114 calculates the above-mentioned errorinfluence R·I by using the current value I and the temperature Tmeasured by the sensors, or the former and the internal DC resistance Rcorresponding to SOC. Based on the calculated R·I, the weight decidingunit 116 decides a weight (W=(1/(1+R·I))) for SOCi and SOCv. Forexample, the weight of SOCv is set to be smaller at a lower value ofSOC, a lower temperature, a larger extent of deterioration, or a largercurrent.

Assuming the weight of SOCv to be W, estimation of SOC in combination ofSOCv and SOCi is executed based on the following formula (12):SOCw=W×SOCv+(1−W)×SOCi  (12)

To calculate SOCw based on the formula (12), a processing unit 110Aincludes a subtracter DF1 for obtaining (1−W), a multiplier MP2 forobtaining (W×SOCv), a multiplier MP1 for obtaining ((1−W)×SOCi), and anadder AD1 for adding outputs of the multipliers MP1 and MP2.

As described above, by obtaining SOCv while modifying the characteristicinformation and combining the obtained SOCv with SOCi based on theweight W depending on R·I, the status detection can be performed withhigh accuracy.

The configuration of a power supply according to a fourth embodiment ofthe present invention will be described below with reference to FIGS.10-12.

FIG. 10 is a block diagram showing the configuration of a power supplyaccording to a fourth embodiment of the present invention. The samereference numerals as those in FIG. 1 denote the same components. FIGS.11A, 11B and 11C are graphs for explaining changes of SOC when anelectricity accumulating unit in the power supply according to thefourth embodiment of the present invention is deteriorated. FIG. 12 is aflowchart showing processing procedures executed by a deteriorationdetermining unit used in the power supply according to the fourthembodiment of the present invention.

In this embodiment, as shown in FIG. 10, a status detecting unit 100Bincludes a deterioration determining unit 150 in addition to theconfiguration shown in FIG. 1. The deterioration determining unit 150periodically monitors the memory unit 130 and determines deteriorationof the electricity accumulating unit 200.

When the electricity accumulating unit 200 is deteriorated, the internalDC resistance R of the electricity accumulating unit 200 is generallyincreased. In the electricity accumulating unit 200 having the increasedinternal DC resistance R, an IR drop caused upon application of thecurrent I becomes larger than that in the initial state of theelectricity accumulating unit 200.

When SOC of the deteriorated electricity accumulating unit 200 isestimated using the characteristic information obtained from theelectricity accumulating unit 200 in the initial state, a discrepancyaway from the theoretical value appears in the estimated result.

As shown in FIG. 11, the SOC exhibits an excessive change as thedeterioration of the electricity accumulating unit 200 progresses. Morespecifically, at the stage where the electricity accumulating unit 200is not deteriorated, when charge is started at a time t1 as shown inFIG. 11A, the change of SOC is within a threshold Th as shown in FIG.11B. With the deterioration of the electricity accumulating unit 200,however, the SOC exhibits an excessive change due to an increase of theinternal DC resistance R, as shown in FIG. 11C, to such an extent thatthe SOC estimated at the start of charge exceeds the threshold Th.

The discrepancy detecting unit 120 detects such an excessive change ofSOC as being a discrepancy away from the theoretical value. If thediscrepancy is detected, the modifying unit 140 modifies thecharacteristic information. In this case, the modifying unit 140 makes amodification to increase the internal DC resistance R and stores theincreased internal DC resistance as new characteristic information inthe memory unit 130.

When the electricity accumulating unit 200 is deteriorated, the statusdetecting unit 100B executes the above-described operation. When theelectricity accumulating unit 200 is further deteriorated, the excessivechange of SOC is detected again and the internal DC resistance R ismodified. In that way, the status detecting unit 100B repeats thoseprocedures as the deterioration of the electricity accumulating unit 200progresses.

The operation of the deterioration determining unit 150 will bedescribed below with reference to FIG. 12. The deterioration determiningunit 150 monitors the characteristic information to be modified.

More specifically, in step S200, the deterioration determining unit 150monitors the characteristic information, e.g., the internal DCresistance R in this embodiment.

Then, in step S210, the deterioration determining unit 150 checkswhether any of values of the internal DC resistance R, which have beencomputed depending on the SOC of the electricity accumulating unit 200,temperature, etc., exceeds the predetermined threshold. If any value ofthe internal DC resistance R exceeds the predetermined threshold, thedeterioration determining unit 150 determines that the electricityaccumulating unit 200 comes to the end of life.

The deterioration determining unit 150 can be constituted as amicroprocessor or a computer. The deterioration determining unit 150 maymonitor the characteristic information by directly accessing the memoryunit 130 as shown in FIG. 10, or may monitor the characteristicinformation read out of the memory unit 130 by the processing unit 110.Further, by providing a display unit associated with the deteriorationdetermining unit 150, the progress of deterioration and the result ofdetermining the end of life can be displayed on a display monitor or thelike.

While the deterioration determining unit 150 is shown in FIG. 10 asbeing installed within the status detecting unit 100B, it may beconstituted in the form of a program module or a subroutine. In thatcase, the deterioration determining unit 150 is stored as software inthe memory unit 130 and executed by the processing unit 110. When thestored software of the deterioration determining unit 150 is executed bythe processing unit 110, the deterioration determining unit 150 monitorsthe characteristic information through the above-described processing bydirectly monitoring the memory unit 130 or reading the characteristicinformation stored in the memory unit 130. The result of determining theend of life of the electricity accumulating unit 200 by thedeterioration determining unit 150 is transmitted to the output unit 400along with the result of the status detection of the electricityaccumulating unit 200. Then, the progress of deterioration and theresult of determining the end of life can be displayed (not shown) onanother microprocessor or computer connected to the output unit 400.

The threshold used by the deterioration determining unit 150 fordetermining the end of life may be set to any desired value, e.g., avalue twice or triple the internal DC resistance of the electricityaccumulating unit 200. As an alternative, the threshold may be decideddepending on the request from a system in which the electricityaccumulating unit 200 is used as a power supply.

According to this embodiment, since the characteristic information ismodified in match with the deterioration of the electricity accumulatingunit 200, the life of the electricity accumulating unit 200 can bequantitatively determined by monitoring the characteristic informationmodified.

The configuration of an initial characteristic extracting device for usewith a power supply according to a fifth embodiment of the presentinvention will be described below with reference to FIGS. 13-15.

FIG. 13 is a block diagram showing the configuration of the initialcharacteristic extracting device for use with the power supply accordingto the fifth embodiment of the present invention. The same referencenumerals as those in FIG. 1 denote the same components.

The initial characteristic extracting device of this embodimentincludes, as shown in FIG. 13, a charging/-discharging unit 500 inaddition to the power supply shown in FIG. 1.

In the power supply shown in FIG. 1, it is assumed that thecharacteristic information, such as the internal DC resistance R and thepolarization voltage Vp of the electricity accumulating unit 200, isstored in the memory unit 130 of the status detecting unit 100 inadvance. The initial characteristic extracting device of this embodimentautomatically determines the characteristic information, such as theinternal DC resistance R and the polarization voltage Vp, for eachelectricity accumulating unit. The determined characteristic informationis stored in another memory unit.

When the extraction of the initial characteristic is completed, theelectricity accumulating unit 200 is assembled into the power supply tooperate as the electricity accumulating unit 200 shown in FIG. 1, andthe characteristic information stored in the other memory unit is alsostored in the memory unit 130 shown in FIG. 1 so that the power supplycan be easily initialized.

In this embodiment shown in FIG. 13, initial values of thecharacteristic information first stored in the memory unit 130 can begiven by any optional values, e.g., the characteristic information ofanother electricity accumulating unit 200, random numbers generated astemporary characteristic information, or all 0.

The charging/discharging unit 500 changes the state of charge (SOC) ofthe electricity accumulating unit 200 by charging and discharging theelectricity accumulating unit 200 in accordance with a predeterminedpulse pattern.

In step S300 of FIG. 14, the charging/discharging unit 500 first chargesthe electricity accumulating unit 200 into an almost fully chargedstate.

Then, in step S310, the charging/discharging unit 500 discharges andcharges the electricity accumulating unit 200 in accordance with thepredetermined pulse pattern. More specifically, as shown in FIG. 15, thecharging/discharging unit 500 discharges the electricity accumulatingunit 200 by applying a discharge pulse P11, and subsequently charges theelectricity accumulating unit 200 by applying a charge pulse P12.

While the charging/discharging unit 500 discharges and charges theelectricity accumulating unit 200, the measuring unit 300 obtainsmeasured values of the electricity accumulating unit 200 during thedischarge and the charge, and the processing unit 110 executes thestatus detection of the electricity accumulating unit 200 based on themeasured values and the optionally given characteristic information.Each time the discrepancy detecting unit 120 detects a discrepancy awayfrom the theoretical value, the modifying unit 140 modifies theoptionally given characteristic information in a repeated manner so thatthe characteristic information is finally converged within a certainrange.

After the lapse of a certain time or after confirmation of theconvergence of the characteristic information, the charging/dischargingunit 500 discharges the electricity accumulating unit 200 in step S320by applying a capacity adjustment pulse P13 shown in FIG. 15, therebylowering the SOC of the electricity accumulating unit 200.

Then, in step S330, it is determined whether the SOC is higher than apredetermined lower limit value, e.g., 0%. If the SOC is higher than thepredetermined lower limit value, the processing of steps S310 and S320is repeated to modify the characteristic information by applying pulsesP21 and P22 shown in FIG. 15.

Then, if the SOC after the capacity adjustment has become lower than thepredetermined lower limit value (e.g., 0%), the processing is brought toan end.

Instead of the above-described procedures, the process of changing theSOC by the charging/discharging unit 500 may be performed by a method offirst setting the SOC of the electricity accumulating unit 200 to 0%,and subsequently repeating charge and discharge for modification andcharge for capacity adjustment such that the electricity accumulatingunit 200 gradually comes into a fully charged state.

Further, by causing the charging/discharging unit 500 to charge anddischarge the electricity accumulating unit 200 while the temperaturestate of the electricity accumulating unit 200 is changed, it is alsopossible to modify the characteristic information depending on thetemperature state of the electricity accumulating unit 200. In such acase, a thermostatic chamber (not shown), for example, is employed tokeep the electricity accumulating unit 200 at a specified temperature.The set temperature of the thermostatic chamber is changed each time theprocess of discharging and charging the electricity accumulating unit200 by the charging/discharging unit 500, described above with referenceto FIG. 14, is completed. The set temperature of the thermostaticchamber may be changed by a manner of gradually raising the temperaturefrom a low to high level or gradually lowering the temperature from ahigh to a low level whenever the discharging and charging process shownin FIG. 14 is completed.

According to this embodiment, as described above, the characteristicinformation can be automatically modified depending on various states,and the initial characteristic of the electricity accumulating unit 200can be extracted.

The configuration of a second initial characteristic extracting devicefor use with a power supply according to a sixth embodiment of thepresent invention will be described below with reference to FIGS. 16 and17.

FIG. 16 is a block diagram showing the configuration of the secondinitial characteristic extracting device for use with the power supplyaccording to the sixth embodiment of the present invention. The samereference numerals as those in FIG. 1 denote the same components. FIGS.17A and 17B are charts for explaining an initial characteristicextracting method in the power supply according to the sixth embodimentof the present invention.

This embodiment includes a charging/discharging unit 510 instead of thecharging/discharging unit 500 shown in FIG. 13. Characteristics of thecharging/discharging unit 510 will be described with reference to FIG.17.

This embodiment further includes a characteristic extracting unit 600.The characteristic extracting unit 600 contains the characteristicinformation regarding the relationship between the electromotive force(OCV) and the state of charge (SOC), and extracts a characteristic ofthe electricity accumulating unit 200 by using measured values obtainedfrom the measuring unit 300.

The charging/discharging unit 510 outputs a current signal having apulse pattern, shown in FIG. 17A, to charge the electricity accumulatingunit 200. A voltage measured at this time is changed as shown in FIG.17B.

The characteristic extracting unit 600 takes in the measured values fora predetermined time while a current I shown in FIG. 17A is applied. Thecharacteristic extracting unit 600 first obtains, from among thetaken-in measured values, a voltage Va immediately before theapplication of the current I. Because the voltage Va represents anelectromotive force (OCV1) of the electricity accumulating unit 200, theSOC of the electricity accumulating unit 200 before the application ofthe current I is determined from the relationship between OCV and SOC,which has been obtained in advance. The voltage Va is taken as a voltagevalue at the timing before an abrupt increase of the current value,while monitoring the current value among the measured values. Also, thecharacteristic extracting unit 600 obtains temperature information amongthe measured values in succession. Thus, the characteristic extractingunit 600 enables the status of the electricity accumulating unit 200,such as the SOC and the temperature, to be automatically detected beforethe application of the current I.

A description is now made of the operation of the characteristicextracting unit 600 when the electricity accumulating unit 200 ischarged with the current I. In general, at the moment when theelectricity accumulating unit 200 is charged with the current I, thevoltage of the electricity accumulating unit 200 is increased by IR.Upon the end of the charge, a voltage drop IR occurs and thereafter adrop of the polarization voltage Vp occurs. In other words, by usingvoltages Vb, Vc and Vd shown in FIG. 17B, the internal DC resistance Rand the polarization voltage Vp can be calculated respectively from thefollowing formulae (13) and (14):R=(Vb−Vc)/1  (13)Vp=Vc−Vd  (14)

Here, because the voltage Vb represents a voltage just before the end ofthe charge with the current I, it can be readily detected by monitoringthe current I. The voltage Vc represents a voltage after the occurrenceof the voltage drop IR. The voltage Vc may be decided in an automaticway as a voltage value after a certain time from the end of the chargewith the current I. An alternative manner is as follows. Generally, whena voltage change after the end of charge of the electricity accumulatingunit 200 exceeds a predetermined threshold, the voltage changerepresents the voltage drop IR, and when that voltage change does notexceed the predetermined threshold, it represents the polarizationvoltage drop. Therefore, when the voltage change not exceeding thepredetermined threshold is detected as a result of monitoring thevoltage value after charging the electricity accumulating unit 200 withthe current I, the voltage at that time can be detected as Vc. Also,because the voltage Vd represents a voltage at a time where the voltagechange has disappeared after the end of the charge with the current I,it can be readily detected by monitoring an amount of the voltagechange. Additionally, the voltage Vd represents an electromotive force(OCV2) of the electricity accumulating unit 200 after the end of thecharge with the current I.

From the characteristic information between the electromotive force(OCV) and the state of charge (SOC), the SOC of the electricityaccumulating unit 200 after being charged for a predetermined time withthe current I can also be readily computed. Further, by using a timefrom the detection of Vc to the detection of Vd, a delay time (timeconstant) τ of the polarization voltage drop can be readily computed.

Moreover, by using an amount of charge J I after the charge for thepredetermined time with the current I, SOC1 obtained from OCV1 beforethe charge, and SOC2 obtained from OCV2 after the charge, a fullycharged capacity Qmax of the electricity accumulating unit 200 can bereadily computed from the following formula (15):Qmax=100×∫I/(SOC2−SOC1)  (15)

The internal DC resistance R, the polarization voltage Vp, the timeconstant τ, and the fully charged capacity Qmax may be determined forone value of the current I, or may be obtained by a manner ofdetermining plural values of each parameter while variously changing thecurrent I and calculating an average of those plural values.

Thus, the characteristic extracting unit 600 can automatically computenot only the present temperature and SOC of the electricity accumulatingunit 200, but also the characteristic information, such as the internalDC resistance R, the polarization voltage Vp, the time constant τ, andthe fully charged capacity Qmax, corresponding to those presentconditions. The computed data of the characteristic information arestored as initial values in the memory unit 130.

Further, by employing the pulse pattern described above with referenceto FIGS. 14 and 15, the characteristic information corresponding tovarious states of charge can be computed. By adjusting the temperatureof the electricity accumulating unit 200 using a thermostatic chamber,the characteristic information corresponding to various temperatures andvarious states of charge of the electricity accumulating unit 200 canalso be computed in an automatic manner.

In addition, by applying the above-described manner of computing thecharacteristic information to the case of discharging the electricityaccumulating unit 200 with the current I, the characteristic informationcorresponding to the temperature and the state of charge of theelectricity accumulating unit 200 during discharge can also be computedin an automatic manner.

The characteristic information computed by the characteristic extractingunit 600 is stored in the memory unit 130. On that occasion, thecharacteristic extracting unit 600 may directly transmit thecharacteristic information to the memory unit 130 for storage therein,as shown in FIG. 16. Alternatively, the characteristic information maybe transmitted to the processing unit 110 such that the processing unit110 stores the characteristic information in the memory unit 130.

The characteristic extracting unit 600 can be constituted as amicroprocessor or a computer executing the above-described processing.

After completing the extraction of the characteristic information asdescribed above, the characteristic extracting unit 600 transmits thereceived measured values, as they are, to the processing unit 110 or thediscrepancy detecting unit 120.

As an alternative, the characteristic extracting unit 600 may beconstituted in the form of a program module or a subroutine executingthe above-described process. In that case, the characteristic extractingunit 600 is stored in the memory unit 130 as software executing theabove-described process, and those procedures are executed by theprocessing unit 110. When the above-described process of thecharacteristic extracting unit 600 is completed, the processing unit 110executes the status detection of the electricity accumulating unit 200by using the characteristic information that has been prepared by thecharacteristic extracting unit 600.

After the processing unit 110 executes the status detection of theelectricity accumulating unit 200 by using the characteristicinformation prepared by the characteristic extracting unit 600, thediscrepancy detecting unit 120 monitors whether there is a discrepancyaway from the theoretical value. Further, the modifying unit 140modifies the characteristic information by the predeterminedmodification amount as described above.

Thus, the provision of the characteristic extracting unit 600 enablesthe initial characteristic information to be automatically determined,the discrepancy detecting unit 120 performs monitoring based on thedetermined characteristic information, and the modifying unit 140modifies the characteristic information. Therefore, the initialcharacteristic can be extracted with high accuracy.

The configuration of a third initial characteristic extracting devicefor use with a power supply according to a seventh embodiment of thepresent invention will be described below with reference to FIGS. 18 and19.

FIG. 18 is a block diagram showing the configuration of the thirdinitial characteristic extracting device for use with the power supplyaccording to the seventh embodiment of the present invention. The samereference numerals as those in FIG. 1 denote the same components. FIG.19 is a chart for explaining an initial characteristic extracting methodin the power supply according to the seventh embodiment of the presentinvention.

This embodiment includes two or more electricity accumulating units 200Aand 200B and a charge/discharge control unit 700 for controlling chargeand discharge of two or more electricity accumulating units 200A and200B.

As shown in FIG. 19, the charge/discharge control unit 700 controlscharge and discharge of currents between the electricity accumulatingunits 200A and 200B. More specifically, the charge/discharge controlunit 700 discharges the electricity accumulating unit 200A and chargesthe electricity accumulating unit 200B with the discharge current fromthe former unit 200A. Also, the charge/discharge control unit 700discharges the electricity accumulating unit 200B and charges theelectricity accumulating unit 200A with the discharge current from theformer unit 200B. When the electricity accumulating units 200A and 200Bof the same type are charged, the voltage in the discharge side may beboosted using a DC/DC converter, etc. Also, when the voltage in thecharge side is lower than that of the electricity accumulating unit inthe discharge side, the voltage in the discharge side may be lowered. Byrepeating the above-mentioned process, charge and discharge can beperformed between the two electricity accumulating units 200A and 200Bin the same manner as that using a pulse pattern.

In operation, charge and discharge are performed between the electricityaccumulating units 200A and 200B, and the measuring unit 300 obtainsmeasured values during the charge and the discharge. The processing unit110 executes the status detection of each electricity accumulating unit200 based on the measured values and the optionally given characteristicinformation. The discrepancy detecting unit 120 monitors whether thereis a discrepancy away from the theoretical value, and the modifying unit140 modifies the optionally given characteristic information. Afterrepeating that process, the finally converged characteristic informationis employed as an initial characteristic of the correspondingelectricity accumulating unit 200.

The electricity accumulating units 200A and 200B may be of the same typeor a combination of different types, such as a lithium ion battery and alead-acid battery, a lithium ion battery and a nickel-hydrogen battery,or a nickel-hydrogen battery and a lead-acid battery. Further, the twoor more electricity accumulating units 200A and 200B may be each of amodular structure including a plurality of electricity accumulatingunits 200 combined with each other.

While the measuring unit 300 for obtaining the measured values of theelectricity accumulating units 200A and 200B is shown only one in FIG.18, it is actually provided for each of the electricity accumulatingunits 200A and 200B to obtain the measured values of the correspondingelectricity accumulating unit. In other words, when there are twoelectricity accumulating units 200, two measuring units 300 are providedto obtain respective measured values of the two electricity accumulatingunits 200 and transmit the measured values to the processing unit 110 orthe discrepancy detecting unit 120.

The characteristic information stored in the memory unit 130 may be onekind of data set when the electricity accumulating units 200A and 200Bof the same type are provided, or may be different specific kinds ofdata sets even when the electricity accumulating units 200A and 200B ofthe same type are provided. Also, the processing procedures stored inthe memory unit 130 to execute the status detection are prepared as onekind of procedures when the electricity accumulating units 200A and 200Bare the same type. When the electricity accumulating units 200A and 200Bare different types, the status detection can also be performed usingone kind of processing procedures common to both the units, or may beperformed using different kinds of processing procedures dedicated forthe respective kinds of the electricity accumulating units 200A and200B.

The processing unit 110 receives the measured values for each of theelectricity accumulating units 200A and 200B, and executes the statusdetection for each of the electricity accumulating units 200A and 200Bby using the characteristic information of the corresponding electricityaccumulating unit, which is stored in the memory unit 130. Theprocessing unit 110 may be provided one common to the plurality ofelectricity accumulating units 200A and 200B, or one dedicated for eachof the electricity accumulating units 200A and 200B.

Similarly to the processing unit 110, the discrepancy detecting unit 120and the modifying unit 140 may be each provided one common to theplurality of electricity accumulating units 200A and 200B, or onededicated for each of the electricity accumulating units 200A and 200B.

With the above-described configuration, the status detection of the twoor more electricity accumulating units 200A and 200B is performed, andwhen the discrepancy detecting unit 120 detects a discrepancy away fromthe theoretical value, the modifying unit 140 modifies thecharacteristic information.

In this way, the initial characteristic of the characteristicinformation can be obtained by performing charge and discharge betweentwo or more electricity accumulating units.

The configuration of a fourth initial characteristic extracting devicefor use with a power supply according to an eighth embodiment of thepresent invention will be described below with reference to FIG. 20.

FIG. 20 is a block diagram showing the configuration of the fourthinitial characteristic extracting device for use with the power supplyaccording to the eighth embodiment of the present invention. The samereference numerals as those in FIG. 1 denote the same components.

In this embodiment, the characteristic extracting unit 600 describedabove with reference to FIG. 16 is additionally associated with theinitial characteristic extracting device shown in FIG. 18. Morespecifically, two or more electricity accumulating units 200A and 200Bare provided, and the charge/discharge control unit 700 performs chargeand discharge between the electricity accumulating units 200A and 200B.The measuring unit 300 obtains measured values during the charge and thedischarge, and the characteristic extracting unit 600 extractscharacteristic information based on an analysis using the measuredvalues. The processing unit 110 executes the status detection for eachof the electricity accumulating units 200A and 200B based on theextracted characteristic information and the measured values. Thediscrepancy detecting unit 120 monitors whether there is a discrepancyaway from the theoretical value, and the modifying unit 140 modifies thecharacteristic information.

In this way, the initial characteristic of the characteristicinformation can be obtained by performing charge and discharge betweentwo or more electricity accumulating units.

According to the present invention, as described above, the state ofcharge of the electricity accumulating unit can be estimated with highaccuracy. Also, the life of the electricity accumulating unit can bequantitatively determined. Further, the initial characteristic of theelectricity accumulating unit can be extracted. These advantageousfeatures are applicable to a wide range of fields including mobileequipment, UPS (Uninterruptible Power Supply), and vehicles such as HEV(Hybrid Electric Vehicle) and EV.

1. A status detector used for a power supply which provides electricityaccumulating means and measuring means for measuring at least current,voltage, and temperature of the electricity accumulating means,comprising: memory means for storing characteristic information of saidelectricity accumulating means; and processing means for executingcalculation for detecting state of charge of said electricityaccumulating means by using information including the measuredinformation obtained from the output of the measuring means and thecharacteristic information which is stored in said memory means; whereinsaid processing means comprises: a first state of charge detecting meansfor obtaining a first state of charge of said electricity accumulatingmeans by using information including an open circuit voltage of saidelectricity accumulating means, and said open circuit voltage isobtained by using information including the measured information and thecharacteristic information; a second state of charge detecting means forobtaining a second state of charge of said electricity accumulatingmeans by using information including the current information of saidelectricity accumulating means obtained from the output of saidmeasuring means; an error detecting means for obtaining a product of acurrent of said electricity accumulating means obtained from the outputof said measuring means, and an internal DC resistance of saidelectricity accumulating means; weight deciding means for obtainingfirst and second weights which weight to said first state of charge andsaid second state of charge by using the product of the current and theinternal DC resistance obtained by said error detecting means; and meansfor obtaining the state of charge of said electricity accumulating meansby combining a state of charge which is obtained by weighting the firstweight to said first state of charge and a state of charge which isobtained by weighting the second weight to said second state of charge.2. The status detector used for the power supply according to claim 1,wherein the first weight is decreased and the second weight is increasedwhen the current of said electricity accumulating means obtained fromthe output of said measuring means is increased or the internal DCresistance of said electricity accumulating means is increased, and thefirst weight is increased and the second weight is decreased when thecurrent of said electricity accumulating means obtained from the outputof said measuring means is increased or the internal DC resistance ofsaid electricity accumulating means is decreased.
 3. The status detectorused for the power supply according to claim 1, further comprising:discrepancy detecting means for detecting the presence of a discrepancyaway from a theoretical value when the state of charge of saidelectricity accumulating means obtained by said processing means ischanged over a predetermined threshold or reversed with respect to themeasured information obtained from the output of said measuring means;and modifying means for modifying the characteristic information storedin said memory means depending on the discrepancy detected by saiddiscrepancy detecting means.
 4. The status detector used for the powersupply according to claim 3, wherein the first weight is decreased andthe second weight is increased when the current of said electricityaccumulating means obtained from the output of said measuring means isincreased or the internal DC resistance of said electricity accumulatingmeans is increased, and the first weight is increased and the secondweight is decreased when the current of said electricity accumulatingmeans obtained from the output of said measuring means is decreased theinternal DC resistance of said electricity accumulating means isdecreased.
 5. A power supply comprising: electricity accumulating means;measuring means for measuring at least current, voltage, and temperatureof said electricity accumulating means; and a status detector fordetecting a state of charge of said electricity accumulating means;wherein said status detector comprises: memory means for storingcharacteristic information of said electricity accumulating means; andprocessing means for executing calculation for detecting state of chargeof said electricity accumulating means by using information includingthe measured information obtained from the output of the measuring meansand the characteristic information which is stored in said memory means;wherein said processing means comprises: a first state of chargedetecting means for obtaining a first state of charge of saidelectricity accumulating means by using information including an opencircuit voltage of said electricity accumulating means, and said opencircuit voltage is obtained by using information including the measuredinformation and the characteristic information; a second state of chargedetecting means for obtaining a second state of charge of saidelectricity accumulating means by using information including thecurrent information of said electricity accumulating means obtained fromthe output of said measuring means; an error detecting means forobtaining a product of a current of said electricity accumulating meansobtained from the output of said measuring means, and for an internal DCresistance of said electricity accumulating means; weight deciding meansfor obtaining first and second weights which weight to said first stateof charge and said second state of charge by using the product of thecurrent and the internal DC resistance obtained by said error detectingmeans; and means for obtaining the state of charge of said electricityaccumulating means by combining a state of charge which is obtained byweighting the first weight to said first state of charge and a state ofcharge which is obtained by weighting the second weight to said secondstate of charge.
 6. The power supply according to claim 5, wherein thefirst weight is decreased and the second weight is increased when thecurrent of said electricity accumulating means obtained from the outputof said measuring means is increased or the internal DC resistance ofsaid electricity accumulating means is increased, and the first weightis increased and the second weight is decreased when the current of saidelectricity accumulating means obtained from the output of saidmeasuring means is decreased or the internal DC resistance of saidelectricity accumulating means is decreased.
 7. The power supplyaccording to claim 5, further comprising: discrepancy detecting meansfor detecting the presence of a discrepancy away from a theoreticalvalue when the state of charge of said electricity accumulating meansobtained by said processing means is changed over a predeterminedthreshold or reversed with respect to the measured information obtainedfrom the output of said measuring means; and modifying means formodifying the characteristic information stored in said memory meansdepending on the discrepancy detected by said discrepancy detectingmeans.
 8. The power supply according to claim 7, wherein the firstweight is decreased and the second weight is increased when the currentof said electricity accumulating means obtained from the output of saidmeasuring means is increased or the internal DC resistance of saidelectricity accumulating means is increased, and the first weight isincreased and the second weight is decreased when the current of saidelectricity accumulating means obtained from the output of saidmeasuring means is decreased or the internal DC resistance of saidelectricity accumulating means is decreased.